1. PDC DRILL BITS

2. Polycrystalline diamond materials for use in polycrystalline diamond compact (PDC) bits, are one of the most important material advances for oil drilling tools in recent years. Fixed-head bits rotate as one piece and contain no separately moving parts. When fixed-head bits use PDC cutters, they are commonly called PDC bits. Since their first production in 1976, the popularity of bits using PDC cutters has grown steadily, and they are nearly as common as roller-cone bits in many drilling applications.

3. Polycrystalline diamond compact (PDC) styles P D Cb i t sa r ed e s i g n e da n dm a n u f a c t u r e d i nt w os t r u c t u r a l l yd i s s i m i l a rs t y l e s Matrix-body bit Steel-body bits Thetwoprovidesignificantlydifferentcapabilities, and, becausebothtypeshavecertainadvantages, achoice betweenthemwouldbedecidedbytheneedsofthe application.

4. Matrix-body “Matrix” is a very hard, rather brittle composite material comprising tungsten carbide grains metallurgically bonded with a softer, tougher, metallic binder. Matrix is desirable as a bit material, because its hardness is resistant to abrasion and erosion. It is capable of withstanding relatively high compressive loads, but, compared with steel, has low resistance to impact loading. Matrix is relatively heterogeneous, because it is a composite material. Because the size and placement of the particles of tungsten carbide it contains vary (by both design and circumstances), its physical properties are slightly less predictable than steel.

5. Steel-body Steel is metallurgically opposite of matrix. It is capable of withstanding high impact loads, but is relatively soft and, without protective features, would quickly fail by abrasion and erosion. Quality steels are essentially homogeneous with structural limits that rarely surprise their users. Design of matrix and steel-body bits Design characteristics and manufacturing processes for the two bit types are, in respect to body construction, different, because of the nature of the materials from which they are made. The lower impact toughness of matrix limits some matrix-bit features, such as blade height. Conversely, steel is ductile, tough, and capable of withstanding greater impact loads. This makes it possible for steel-body PDC bits to be relatively larger than matrix bits and to incorporate greater height into features such as blades.

6. ADVANTAGE OF MATRIX-BODY PDC BITS Matrix-bodyPDCbitsarecommonlypreferredoversteel-bodybitsfor environmentsinwhichbodyerosionislikelytocauseabittofail. Fordiamond- impregnatedbits, onlymatrix-bodyconstructioncanbeused. ADVANTAGE OF STEEL-BODY PDC BITS Thestrengthandductilityofsteelgivesteel-bitbodieshighresistanceto impactloading. Steelbodiesareconsiderablystrongerthanmatrixbodies. Becauseofsteelmaterialcapabilities, complexbitprofilesandhydraulic designsarepossibleandrelativelyeasytoconstructonamulti-axis, computer- numerically-controlledmillingmachine. Abeneficialfeatureofsteelbitsisthat theycaneasilyberebuiltanumberoftimesbecausewornordamagedcutters canbereplacedrathereasily. Thisisaparticularadvantageforoperatorsinlow- costdrillingenvironments.

7. DEVELOPMENT OF PDC BITS Fortunately, bothsteelsandmatrixarerapidly evolving, andtheirlimitationsarediminishing. Ashard-facingmaterialsimprove, steelbitsare becomingextremelywellprotectedwith materialsthatarehighlyresistanttoabrasion anderosion. Atthesametime, thestructural andwear-resistingpropertiesofmatrixmaterials arealsorapidlyimproving, andtherangeof economicapplicationssuitableforbothtypesis growing. Today’smatrixhaslittleresemblancetothatof evenafewyearsago. Tensilestrengthsand impactresistancehaveincreasedbyatleast 33%, andcutterbrazestrengthhasincreasedby ≈80%. Atthesametime, geometriesandthe technologyofsupportingstructureshave improved, resultinginstrong, productivematrix products.

8. ARTICLE SOURCE: H T T P : / / P E T R O W I K I . O R G / P D C _ D R I L L _ B I T S IMAGE SOURCE: H T T P : / / W W W . H A R D M E T A L S . C O M /